For over 40 years, the Glasgow Coma Scale (GCS)1 has played a major role in the clinical assessment and management of patients with reduced level of consciousness. Its assessment of motor, verbal, and eye responses enables characterization of patients and guides diagnostic (eg, CT scanning) and therapeutic interventions. The GCS is used by both prehospital and clinical practitioners from different disciplines and, although developed for use in traumatic brain injury (TBI) patients, is broadly applicable to patients with a reduced level of consciousness due to other causes.2 Reliable scoring of the GCS is fundamental to the practical utility of the scale. While we recognize that different aspects of reliability may be differentiated (inter-rater, intrarater agreement, and internal consistency), the feature most relevant to the use of the GCS in the clinical setting relates to interobserver agreements.

While others have criticized the GCS and questioned its general applicability,3-7 we found adequate interobserver reliability in good-quality studies identified in a systematic review on the reliability of GCS assessments.8 This is relevant to its potential use for transfer of clinical information on a multidisciplinary level. Substantial heterogeneity, however, existed between studies and reliability estimates varied. Reliability tends to vary across different studies due to differences in study characteristics,9 which can affect the estimates of reliability. The reliability also depends on how the GCS assessments are described, being higher for the 3 components of the scale than for the derived sum score.8